Method and apparatus for decoding random access response message in wireless communication system

ABSTRACT

The present disclosure relates to a communication technique for converging an IoT technology with a 5G communication system for supporting a higher data transmission rate beyond a 4G system, and a system therefor. The present disclosure may be applied to an intelligent service (for example, a smart home, a smart building, a smart city, a smart car or connected car, healthcare, digital education, retail business, a security and security related service, or the like) on the basis of a 5G communication technology and an IoT related technology. A method for a terminal according to the present disclosure comprises the steps of transmitting a random access preamble through a resource associated with a resource through which a downlink synchronization signal has been received; receiving a random access response message to the random access preamble; and decoding the random access response message by using information determined on the basis of the resource through which the downlink synchronization signal has been received.

TECHNICAL FIELD

Various embodiments of the present disclosure relate to a method fordecoding a random access response message in a wireless communicationsystem, and more particularly, to a method for decoding a random accessresponse message using a relationship between a random access preamblemessage and a random access response message during a random accessprocedure.

BACKGROUND ART

To meet the demand for wireless data traffic having increased sincedeployment of 4 G communication systems, efforts have been made todevelop an improved 5 G or pre-5 G communication system. Therefore, the5 G or pre-5 G communication system is also called a ‘Beyond 4 GNetwork’ or a ‘Post LTE System’. The 5 G communication system isconsidered to be implemented in higher frequency (mmWave) bands, e.g.,60 GHz bands, so as to accomplish higher data rates. To decreasepropagation loss of the radio waves and increase the transmissiondistance, the beamforming, massive multiple-input multiple-output(MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beamforming, large scale antenna techniques are discussed in 5 Gcommunication systems. In addition, in 5 G communication systems,development for system network improvement is under way based onadvanced small cells, cloud Radio Access Networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, Coordinated Multi-Points(CoMP), reception-end interference cancellation and the like. In the 5 Gsystem, Hybrid FSK and QAM Modulation (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5 Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5 G technology and the IoT technology.

On the other hand, when different terminals transmit the same randomaccess preamble, the base station cannot identify between differentterminals. Therefore, the base station transmits one random accessresponse, and the terminal receives the same random access response. Therandom access response may include uplink resource allocationinformation, and the terminal may transmit a radio resource control(RRC) connection request message through the same uplink resource. Themessage may act as interference from the viewpoint of the base station.Therefore, there is a need for a method for setting a relationshipbetween a random access preamble and a random access response messageand transmitting different random access responses to differentterminals even when the terminal transmits the same random accesspreamble.

DISCLOSURE OF INVENTION Technical Problem

An object of the present disclosure is directed to provision of a methodfor setting a relationship between a random access preamble and a randomaccess response message in a random access procedure and transmittingdifferent random access responses to different terminals even when aterminal transmits the same random access preamble.

Solution to Problem

Various embodiments of the present disclosure are directed to theprovision of a method of a terminal in a wireless communication system,including: transmitting a random access preamble through a resourceassociated with a resource receiving a downlink synchronization signal;receiving a random access response message for the random accesspreamble; and decoding the random access response message usinginformation determined based on the resource receiving the downlinksynchronization signal.

Various embodiments of the present disclosure are directed to theprovision of a method of a base station in a wireless communicationsystem, including: receiving a random access preamble through a resourceassociated with a resource transmitting a downlink synchronizationsignal; and transmitting a random access response message based on theresource transmitting the downlink synchronization signal, wherein therandom access response message is decoded using information determinedbased on a resource receiving the downlink synchronization signal.

Various embodiments of the present disclosure are directed to theprovision of a terminal in a wireless communication system, including: atransceiver configured to transmit and receive a signal; and acontroller configured to transmit a random access preamble through aresource associated with a resource receiving a downlink synchronizationsignal; receive a random access response message to the random accesspreamble; and decode the random access response message by usinginformation determined based on the resource receiving the downlinksynchronization signal.

Various embodiments of the present disclosure are directed to theprovision of a base station in a wireless communication system,including: a transceiver configured to transmit and receive a signal;and a controller configured to receive a random access preamble througha resource associated with a resource transmitting a downlinksynchronization signal, and transmit a random access response messagebased on a resource transmitting the downlink synchronization signal,wherein the random access response message is decoded using informationdetermined based on a resource receiving the downlink synchronizationsignal.

Advantageous Effects of Invention

According to the present disclosure, it is possible for each terminal toreceive different random access response messages even if differentterminals transmit the same random access preamble by setting therelationship between the random access preamble and the random accessresponse message.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a random access procedure in LTE.

FIG. 2 is a diagram illustrating a random access procedure in abeamforming-based system according to the present disclosure.

FIG. 3A is a diagram illustrating a method for transmitting a firstmessage according to beam reciprocity in the beamforming based systemaccording to the present disclosure.

FIG. 3B is a diagram illustrating in detail a process of transmitting afirst message shown in FIG. 2.

FIG. 4 is a diagram illustrating various RACH preamble formats accordingto the present disclosure.

FIG. 5 is a diagram showing an embodiment in which only one FFT is usedwhen the RACH and a data channel are multiplexed.

FIG. 6 is a diagram illustrating a case where FFT having different sizesare used while using preamble format 2-1.

FIG. 7 is a diagram illustrating an embodiment of setting an RACHtransmission occasion for a predetermined interval according to thepresent disclosure.

FIG. 8 is a diagram illustrating a random access procedure (RAprocedure) according to a first method for establishing a relationshipbetween MSG2 and MSG1.

FIG. 9 is a diagram illustrating a method for allowing an RACH resourceto include Tx beam information.

FIGS. 10A and 10B are diagrams showing a method for setting a timebetween MSG2 and the MSG1.

FIG. 11 is a diagram illustrating a relationship between MSG1 and MSG2depending on a preamble ID according to an embodiment of the presentdisclosure.

FIG. 12 is a diagram illustrating a relationship between the MSG1 andthe MSG2 depending on RA-RNTI according to an embodiment of the presentdisclosure.

FIG. 13 is a diagram illustrating an operation sequence of a terminalaccording to an embodiment of the present disclosure.

FIG. 14 is a diagram illustrating an operation sequence of a basestation according to an embodiment of the present disclosure.

FIG. 15 is a diagram illustrating a structure of the terminal accordingto an embodiment of the present disclosure.

FIG. 16 is a diagram illustrating a structure of the base stationaccording to an embodiment of the present disclosure.

MODE FOR THE INVENTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

In describing the embodiments of the present disclosure, a descriptionof technical contents which are well known to the art to which thepresent disclosure belongs and are not directly connected with thepresent disclosure will be omitted. This is to more clearly transfer agist of the present disclosure by omitting an unnecessary description.

For the same reason, some components are exaggerated, omitted, orschematically illustrated in the accompanying drawings. Further, thesize of each component does not exactly reflect its real size. In eachdrawing, the same or corresponding components are denoted by the samereference numerals.

Various advantages and features of the present disclosure and methodsaccomplishing the same will become apparent from the following detaileddescription of embodiments with reference to the accompanying drawings.However, the present disclosure is not limited to the embodimentsdisclosed herein but will be implemented in various forms. Theembodiments have made disclosure of the present disclosure complete andare provided so that those skilled in the art can easily understand thescope of the present disclosure. Therefore, the present disclosure willbe defined by the scope of the appended claims. Like reference numeralsthroughout the description denote like elements.

In this case, it may be understood that each block of processing flowcharts and combinations of the flow charts may be performed by computerprogram instructions. Since these computer program instructions may bemounted in processors for a general computer, a special computer, orother programmable data processing apparatuses, these instructionsexecuted by the processors for the computer or the other programmabledata processing apparatuses create means performing functions describedin block(s) of the flow charts. Since these computer programinstructions may also be stored in a computer usable or computerreadable memory of a computer or other programmable data processingapparatuses in order to implement the functions in a specific scheme,the computer program instructions stored in the computer usable orcomputer readable memory may also produce manufacturing articlesincluding instruction means performing the functions described inblock(s) of the flow charts. Since the computer program instructions mayalso be mounted on the computer or the other programmable dataprocessing apparatuses, the instructions performing a series ofoperation steps on the computer or the other programmable dataprocessing apparatuses to create processes executed by the computer tothereby execute the computer or the other programmable data processingapparatuses may also provide steps for performing the functionsdescribed in block(s) of the flow charts.

In addition, each block may indicate some of modules, segments, or codesincluding one or more executable instructions for executing a specificlogical function(s). Further, it is to be noted that functions mentionedin the blocks occur regardless of a sequence in some alternativeembodiments. For example, two blocks that are contiguously illustratedmay be substantially simultaneously performed in fact or be performed ina reverse sequence depending on corresponding functions sometimes.

Here, the term ‘-unit’ used in the present embodiment means software orhardware components such as FPGA and ASIC and the ‘˜unit’ performs anyroles. However, the meaning of the ‘˜unit’ is not limited to software orhardware. The ‘˜unit’ may be configured to be in a storage medium thatmay be addressed and may also be configured to reproduce one or moreprocessors. Accordingly, for example, the ‘˜unit’ includes componentssuch as software components, object oriented software components, classcomponents, and task components and processors, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuit, data, database, data structures, tables, arrays, andvariables. The functions provided in the components and the ‘˜units’ maybe combined with a smaller number of components and the ‘˜units’ or maybe further separated into additional components and ‘˜units’. Inaddition, the components and the ‘˜units’ may also be implemented toreproduce one or more CPUs within a device or a security multimediacard.

Further, in the drawings illustrating a method in embodiments, the orderof description does not necessarily correspond to the order ofexecution, and the order relationship may be changed or executed inparallel.

In addition, the present disclosure describes, by way of example, a caseof a wireless communication system for convenience of explanation, butthe content of the present disclosure may also be applied to a wiredcommunication system.

FIG. 1 is a diagram illustrating a random access procedure in LTE.

A base station cannot know which terminal is connected at the time of aninitial access. Therefore, a terminal attempting to access a networkthrough power-on or handover may first acquire downlink synchronizationthrough a downlink synchronization signal (SS).

Referring to FIG. 1, in step S110, the terminal may receive the downlinksynchronization signal. The terminal may perform synchronization usingthe downlink synchronization signal.

In step S120, the terminal may transmit a random access preamble to thebase station. In the present disclosure, a message which transmits therandom access preamble may be referred to as a first message or MSG1.

Specifically, the terminal may acquire random access channelconfiguration (RACH configuration) information transmitted through adownlink broadcast signal (broadcast channel (BCH)/system informationblock (SIB) or the like), and select any random access (RA) sequencebased on the acquired RACH configuration information and transmit theselected random access sequence to the base station (MSG1).

In step S130, the base station receiving the random access preamble maytransmit a random access response (RAR) message (hereinafter, referredto as a second message or MSG2) to the terminal.

Specifically, the base station may detect the RACH from each terminaland transmit a random access response message including resourceallocation information for uplink transmission to the terminal (MSG2).

The resource to which the random access response is transmitted may beindicated by DCI transmitted on PDCCH, and the DCI may be scrambledusing RA-RNTI (may be addressed to the RA-RNTI on the PDCCH). Also, therandom access response message may include at least one of informationon a physical ID generated based on a preamble identifier, informationrelated to time alignment, initial uplink grant information (uplinkresource allocation information), and temporary C-RNTI.

The terminal may transmit the random access preamble (or a PRACHpreamble), and determine that the transmission fails when not receivinga response from the base station for a predetermined time and retransmitthe random access preamble.

On the other hand, in step S140, the terminal receiving the randomaccess response message from the base station may transmit an RRCconnection request message (may be referred to as a third message orMSG3) to the base station.

The terminal may transmit a third message using an uplink resource whichis configured from the base station, and the terminal may transmit amessage for its own unique ID and RRC connection to the third message.

In step S150, the base station detecting the message may transmit RRCsetup information to the terminal. This may allow the base station toperform contention resolution. In this case, early contention resolutionaddressed to temporary C-RNTI for initial access can be made. However,in a non-contention based random access procedure such as handover, onlythe steps S120 and S130 in the above procedure may be performed.

Meanwhile, the case in which a collision occurs during the random accessprocedure is as follows.

In the procedure of transmitting the first message MSG1, two differentterminals may select the same RA sequence (or the RACH sequence) andtransmit the selected RA sequence to the base station. The base stationmay detect the RACH sequences transmitted from different terminals, butthe base station cannot identify between different terminals because theRA sequences transmitted by the terminal are the same.

Therefore, the base station transmits only one second message (MSG2)corresponding to the RA sequence, so that the two different terminalsall receive the same MSG2.

Therefore, the two different terminals transmit the third message MSG3using the same uplink resource allocated through the same MSG2. When thebase station receives MSG3 from different terminals, the two MSG3 mayinterfere with each other.

Accordingly, the present disclosure proposes a method for establishing arelationship between MSG1 and MSG2 to reduce collision probability in abeamforming based random access procedure so that a base stationtransmits different MSG2 to different terminals even when the terminalstransmit the same MSG1.

FIG. 2 is a diagram illustrating a random access procedure in abeamforming-based system according to the present disclosure.

The embodiment shown in FIG. 2 shows the random access procedure on theassumption that there is no beam reciprocity. The beam reciprocity meansthat the base station or the terminal may use a reception beam as atransmission beam or use the transmission beam as the reception beam.That is, the situation in which there is no beam reciprocity mayrepresent that a beam used for downlink reception may not be used as atransmission beam for uplink transmission or a beam used for uplinkreception may not be used as a transmission beam for downlinktransmission.

Referring to FIG. 2, the base station may transmit the downlinksynchronization signal every frame in step S210. At this time, the basestation may transmit the downlink synchronization signal while alteringthe transmission beam in the frame. The terminal may detect the downlinksynchronization signal while altering the reception beam every frame.

The terminal that detects the downlink synchronization signal selectsthe RA sequence for random access.

In step S220, the terminal may transmit the random access preamblemessage (first message). At this time, the terminal may repeatedlytransmit the first message so that the base station can receive thefirst message using all of the reception beams.

FIG. 3A is a diagram illustrating a method for transmitting a firstmessage according to beam reciprocity in the beamforming based systemaccording to the present disclosure.

As described above, the situation where there is no beam reciprocitymeans the state in which the beam used for the downlink reception maynot be used as the transmission beam for the uplink transmission, or thebeam used for the uplink reception may not be used as the transmissionbeam for the downlink transmission, and the beam reciprocity may be usedin combination with the term ‘beam correspondence’.

The terminal may receive the downlink synchronization signal of the basestation and measure the received downlink synchronization signal todetermine the transmission beam of the base station having the strongestsignal strength. At this time, if the beam correspondence exists, theterminal may assume that the transmission beam is used as the receptionbeam, thereby selecting an RACH resource 310 corresponding to thereception beam of the base station (UE Tx config. 1). Accordingly, theterminal may transmit the first message on the selected RACH resource310.

On the other hand, when the beam correspondence does not exist, theterminal may transmit the first message to all the reception beams ofthe base station (UE Tx config. 2). At this time, the terminal mayrepeatedly transmit the first message using a fixed beam, and the beamof the terminal may be determined according to whether the terminal hasthe beam correspondence.

For example, when the terminal has the beam correspondence, the terminalmay transmit the first message using the beam that receives the downlinksynchronization signal. On the other hand, when the terminal does nothave the beam correspondence, the terminal may transmit the firstmessage using any beam. However, the embodiment of the presentdisclosure is not limited thereto, and may use a method that allows aterminal to transmit a first message by selecting any beam regardless ofbeam correspondence of the terminal, and alters and transmits a beamwhen the terminal fails to receive a second message.

An occasion in which the terminal transmits the first message may bereferred to as a RACH transmission occasion, and the RACH transmissionoccasion may include one symbol or a plurality of symbols.

That is, according to the present disclosure, one RACH preamble formatcan be transmitted in the RACH transmission occasion, in which the RACHpreamble format may transmit single or multiple RACH preambles. Onepreamble is composed of one or a plurality of RACH sequences, and theRACH sequence is composed of one or a plurality of RACH symbols.

FIG. 3B is a diagram illustrating in detail a process of transmitting afirst message shown in FIG. 2.

As shown in FIG. 3B, a resource capable of transmitting a RACH preambleformat is associated with a downlink signal or channel (DLsignal/channel). At this time, as can be seen in FIG. 3B, one downlinksignal or channel may be associated with one RACH resource, and aplurality of downlink signals or channels may be associated with oneRACH resource. Also, although not shown in the figure, one downlinksignal or channel may be associated with a plurality of RACH resources.

At this time, the downlink signal or channel may mean a synchronizationsignal, a reference signal, or a broadcast channel. Accordingly, thefact that the downlink signal or channel can be associated with the RACHresource means that the downlink signal is received or the resource onwhich the channel is located can be associated with the RACH resource.

Referring to FIG. 3B, a downlink signal or channel 1 331 may beassociated with a subset 341 of RACH resource, and a downlink signal orchannel 2 332 may be associated with a subset 342 of RACH resource. Thisshows an example in which one occasion for DL signal/broadcast channelfor a downlink signal or channel is associated with a subset of one RACHresource.

In addition, downlink signal or channels 3 and 4 333 and 334 may beassociated with a subset 343 of RACH resources. This shows an example inwhich multiple occasions for DL signal/broadcast channel for thedownlink signal or channel is associated with a subset of one RACHresource.

Accordingly, the terminal may select a subset of RACH resources usingthe downlink measurement and the corresponding relationship.

At this time, the subset of RACH resources may be composed of one or aplurality of RACH resources. The present disclosure is described on theassumption that the subset of RACH resources is composed of one RACHresource. In such a case, the subset of RACH resources may be used asthe same concept as the RACH resource. However, the embodiment of thepresent disclosure is not limited thereto, and the present disclosuremay similarly be applied to the case in which the subset of RACHresources is composed of a plurality of RACH resources.

If there is no beam reciprocity, when a specific DL signal/channel isdetected, the terminal may select the corresponding RACH resource andtransmit the RACH preamble format.

At this time, the terminal may transmit single or multiple/repeatedpreamble(s) during the RACH transmission occasion using the sametransmission beam (during a RACH transmission occasion of single ormultiple/repeated preamble(s), UE uses the same UE Tx beam).

On the other hand, if there is the beam reciprocity, when the terminaldetects the downlink signal or channel 2 332, the terminal may transmitthe RACH preamble format in the RACH resource 342 which corresponds tothe downlink signal, the broadcast information (BCH) decoded after thedetection of the downlink signal or the channel 2 332.

On the other hand, the RACH preamble format is composed of single ormultiple RACH preamble(s), and the RACH preamble is composed of singleor a plurality of RACH sequences and CPs. The RACH sequence is composedof one or a plurality of RACH OFDM symbols.

The RACH OFDM symbol may have one or a plurality of subcarrier spacingvalues. That is, in the case of operating in a low frequency band, anRACH OFDM symbol (RACH symbol) having a short subcarrier spacing withrespect to a data channel as in the LTE may be considered, and in thecase of operating in a high frequency band, an RACH OFDM symbol having asubcarrier spacing similar to a data channel in consideration of phasenoise may be considered. In the case of considering an RACH OFDM symbolhaving a short length, the repeated transmission can be made forcoverage extension.

To this end, the RACH preamble format may be classified as shown in FIG.4. Here, unlike the format shown in FIG. 4, a general RACH preambleformat may be represented as follows.

TABLE 1 Preamble format 

T_(CP) 

T_(GP) 

T_(SEQ) 

Note 

1 

M · T_(s) 

G · T_(s) 

N · T_(s) 

T_(s): 1/(Δf × N_(FFT)), Δf: subCarrier spacing, N_(FFT): FFT size 

M should be longer than round-trip delay 

N is length for RACK sequence 

G is the length of guard interval 

Here, Ts represents one sample duration in a time domain. M represents alength of a cyclic prefix CP, G represents a length of a guard intervalGT, and N is the number of samples of an RACH preamble length. In thiscase, the G may mean the number of time domain samples corresponding toGT/Ts.

FIG. 4 is a diagram illustrating various RACH preamble formats accordingto the present disclosure.

FIG. 4 shows an example for various RACH preamble formats 2. Referringto FIG. 4, in option 1 (Format 2-1), the preamble format may beconfigured so that the CP and the GT are inserted and the RACH preambleis repeatedly transmitted.

Also, in option 2 (Format 2-2), the preamble format may be configured sothat the CP and the RACH sequence are repeatedly transmitted in pairs,and the GT is inserted at the end.

Also, in option 3 (Format 2-3), the preamble format may be configured sothat the CP, the RACH sequence, and the GT are repeatedly transmitted inpairs.

Also, in option 4 (Format 2-4), the preamble format may be configured toconfigure and repeatedly transmit the RACH preamble with different RACHsequences in the option 2 (Format 2-2).

Also, in option 5 (Format 2-5), the preamble format may be configured toconfigure and repeatedly transmit the RACH preamble with different RACHsequences in the option 3.

The RACH preamble format 2 may be configured as at least one of theabove-described formats 2-1 to 2-5. Alternatively, at least one of theabove-described formats 2-1 to 2-5 may be used in a separate format,respectively.

On the other hand, the preamble format shown in the Format 2-1 can berepresented as shown in Table 2 below. In Table 2, k is a parameterindicating the repeated transmission, and may be transmitted to theterminal through the SIB/MIB or a higher layer signal.

TABLE 2 Preamble format 2-1 Preamble format 

T_(CP) 

T_(GP) 

T_(SEQ) 

Note 

2-1 

M · T_(s) 

G · T_(s) 

K · N · T_(s) 

A UE transmits consecutive ‘K’ RACH symbols during RACH occasion. Thevalue of K should be indicated to UE via higher layer signalling 

The option shown in Format 2-1 is advantageous in that data channeldecoding and RACH may be detected using only one FFT when the datachannel and the RACH are multiplexed.

FIG. 5 is a diagram showing an embodiment in which only one FFT is usedwhen the RACH and a data channel are multiplexed.

As shown in FIG. 5, an FFT window is adjusted to detect the datachannel. In this case, since the preamble format is repeated without theCP, orthogonality between preamble OFDM symbols is not broken.Accordingly, using the FFT window to decode the data channel, the RACHsymbol can be detected with only phase rotation being generated.However, when only one FFT is used, there is a disadvantage that a guardinterval is included between the beam and the beam.

FIG. 6 is a diagram illustrating a case where FFT having different sizesare used while using preamble format 2-1.

As in the embodiment shown in FIG. 5, when FFT for decoding a datachannel is performed, data may be decoded without inter-channelinterference due to RACH OFDM symbols having the repeatedcharacteristics of the preamble format 2-1. However, when the same FFTis applied to detect the RACH, the orthogonality of the data channel isbroken and the inter-channel interference occurs. Therefore, when theRACH is detected, a band in which the RACH is transmitted is firstfiltered in the same manner as LTE, and the FFT is performed on thecorresponding RACH. In the case of detecting the RACH in this manner,there is an advantage that the guard time between the beams is notneeded since there is no need to match the beam to the data channel asshown in FIG. 5.

On the other hand, the classified preamble formats 2-2 and 2-3 aredifferent from preamble format 2-1 in that the CP between the RACHpreambles is inserted. Therefore, an orthogonal cover code (OCC) may beapplied over various RACH OFDM symbols or RACH sequences as a method forincreasing capacity.

For example, assuming that two RACH sequences are repeated, the RAcapacity may be increased using OCCs of [1 1] and [1 −1] while using thesame RA sequence.

When the preamble format 2-1 is used, the capacity may be increased bythe cyclic prefix in a frequency domain. For example, assuming that alength of RACH sequence for the preamble format 2-1 is N and thesequence mapped in the frequency domain is x, that is, when RACHsequences of x[0], . . . , x[N−1] are considered, a first terminal mayuse RA sequence of x[0], x[1], . . . , x[N−2], x[N−1] and a secondterminal may use an extended RA sequence using cyclic prefixes of x[1],x[2], . . . , x[N−1], x[0].

On the other hand, the subset of the RACH resource may be composed ofone or a plurality of RACH resources.

In the subset of one RACH resource, the transmission and reception beamsof the terminal and the base station may be fixed. Also, as describedabove, the subset of one RACH resource may be associated with one or aplurality of DL signals/channel occasions.

In addition, as described above, when the base station does not havebeam reciprocity, the terminal transmits the RACH preamble over a subsetof all RACH resources so that the base station may detect the RACH whilealtering the receive beam, and when the base station has beamreciprocity, one or multiple RACH preambles may be transmitted byselecting the subset of RACH resources corresponding to the DLsignal/channel estimated on the downlink.

The terminal may transmit a plurality of RACHs during one RACHtransmission occasion, as in the case where there is no beamreciprocity. In this case, the base station may receive the plurality ofRACHs while altering the beam of the base station. At this time, even ifthe detected RACHs all have the same RACH preamble ID (preamble ID), thebase station may not assume that the detected RACH preamble ID istransmitted from one terminal. That is, the base station may notidentify whether the plurality of detected RACHs are RACHs transmittedfrom one terminal or RACHs transmitted from a plurality of terminals.Here, the base station may consider the following method fortransmitting a random access response.

1-1. The base station may transmit one RAR on the assumption that it hasreceived a plurality of received RACHs from one terminal. The RAR mayinclude grant information, and the grant information may include uplinkresource allocation information for transmitting MSG3. Also, the RAR mayinclude timing information for uplink synchronization. When transmittinga single RAR, the base station should determine which timing informationshould be included.

1-1-1. The base station may include the timing information in the RARbased on the RACH signal having the largest signal.

1-1-2. The base station may include the timing information in the RARbased on the RACH signal having the largest propagation delay. Based onthe timing at which the propagation delay is largest, it means that theterminal may transmit the uplink signal at the earliest time, and theMSG3 transmission does not collide with the downlink transmission signalof the base station. However, the earlier timing information isdetermined so that the base station does not exceed the CP range.

1-1-3. The base station may detect timing information detected from aplurality of RACH signals and classify the timing information into asimilar timing-group. When the classified timing group forms a pluralityof groups, the base station may adopt a group having the largest timinggroup element and include timing information corresponding to the groupin the RAR.

2-1. The terminal receiving one RAR may transmit one MSG3.

On the other hand, unlike the assumption of the above 1-1, if it isassumed that a plurality of received RACHs are received from a pluralityof terminals, the base station may transmit a plurality of RARs. In thiscase, the terminal can receive the plurality of RARs.

2-2. The terminal receiving the plurality of RARs may operate as followsdepending on which RAR of the plurality of PARs is selected.

2-2-1. The terminal may transmit the MSG3 by selecting the RAR havingthe largest SNR among the plurality of RARs.

2-2-2. The terminal may transmit the MSG3 by selecting the RAR havingthe largest timing advance value among the plurality of RARs. Asdescribed above, based on the timing at which the propagation delay islargest, it means that the terminal may transmit the uplink signal atthe earliest time, and the MSG3 transmission does not collide with thedownlink transmission signal of the base station. However, the earliertiming information is determined so that the base station does notexceed the CP range.

2-2-3. The terminal may form a timing group according to timinginformation among the plurality of RARs, and select a group having thelargest timing information among a plurality of timing groups formed,select a RAR based on the group, and transmit the MSG3.

Also, when there is no beam reciprocity, the base station may set aplurality of RACH transmission occasions for a predetermined interval toreduce the total RA time.

FIG. 7 is a diagram illustrating an embodiment of setting an RACHtransmission occasion for a predetermined interval according to thepresent disclosure.

Referring to FIG. 7, the base station of the present disclosure may seta density of the RACH transmission for a predetermined interval. Thatis, one or a plurality of RACH transmission occasions may be allocatedfor a predetermined interval before the terminal receives the randomaccess response message.

When the terminal may use the reception beam as the transmission beam,the first message may be transmitted using the beam receiving thedownlink synchronization signal, but when the terminal may not use thereception beam as the transmission beam, the first message may betransmitted while the beam is altered. As described above, when theterminal may not use the reception beam as the transmission beam, theterminal attempt to receive the second message after transmitting thefirst message using one beam, and when the terminal fails to receive thesecond message, the terminal may repeat a process of attempting totransmit the first message using another beam and then receive thesecond message.

When using such a method, it may take a long time. Therefore, a methodfor transmitting a first message while altering a beam in a plurality ofRACH transmission occasions before a second message is received may beconsidered.

Therefore, the terminal may transmit the random access preamble on theRACH while altering the transmission beam every RACH transmissionoccasion. At this time, the base station may transmit the random accessresponse message (MSG2) to the terminal for the detected random accesspreamble, and it is necessary to identify to which the MSG1 the MSG2corresponds.

In order to establish the relationship between the MSG2 and the MSG1,the following methods may be considered.

The first method for establishing the relationship between MSG2 and MSG1is based on the current LTE scheme and may be used for scheduling of thebase station.

FIG. 8 is a diagram illustrating a random access procedure (RAprocedure) according to a first method for establishing a relationshipbetween MSG2 and MSG1.

FIG. 8 is a diagram showing an RA procedure considering two UEsaccording to an embodiment of the present disclosure. Here, it isassumed that the terminal identically selects a preamble ID of the RACHpreamble (e.g., Preamble 0). At this time, since the preamble sequenceis generated by the preamble identifier, it can be regarded as the sameconcept. That is, the preamble identifier of the present disclosure maymean a preamble sequence. Accordingly, the preamble 0 may mean apreamble sequence corresponding to index 0 among a plurality of preamblesequences. For example, if 64 preamble sequences are generated, thepreamble 0 may mean a first preamble sequence.

UE 0 transmits a random access preamble having a Preamble ID 0 using aUL Tx beam 0 on a PRACH, and UE 1 transmits the random access preamblehaving the preamble ID 0 using an uplink transmission beam (UL Tx beam)x on the PRACH.

The base station (hereinafter, gNB) may detect a preamble (or RACH)transmitted from the UE0 and the UE1 using different receive (Rx) beams.

The gNB detects the preamble (or RACH) having the preamble ID 0 usingdifferent Rx beams, but may not determine whether the preamble istransmitted from different terminals or the preamble transmitted fromthe same terminal undergoes a multi-channel environment.

Accordingly, the gNB transmits a RAR including a PID (Physical ID) 0based on the detected Preamble ID 0. That is, the base station maytransmit a response message 0 having PID 0 to the terminal, and the UE0and UE1 may each detect the response message 0 having the PID 0. At thistime, UE0 and UE1 may receive response message 0 using the selectedreceive beam while receiving a DL SS/BCH/beam reference signal (BRS)(the DL RX beam chosen during a group of DL SS/BCH/BRS). Therefore, eachterminal that detects a RAR having PID 0 transmits the MSG3 using thesame UL Tx beam on the assumption that the previous MSG1 transmissionsucceed.

In this case, the two MSG3 signals transmitted by the UE0 and the UE1may interfere with each other and thus the gNB may not detect any MSG3.Therefore, two UEs may not receive an acknowledgment message (alsocalled an Ack message, or MSG4) for the MSG3.

Alternatively, the gNB may detect only one of the two MSG3 s. In thiscase, a process of preventing one UE from being accessed to the gNB andtransmitting the MSG1 again is performed.

Referring to FIG. 8, the case in which the base station detects the MSG3transmitted by the UE1 will be described by way of example. Therefore,the base station may transmit the MSG4 including UE ID 1 to theterminal. Accordingly, the UE1 may access the base station.

However, the UE0 may not access the base station, and the UE0 may alterthe transmission beam (UL Tx beam) at the next RACH occasion andtransmit the preamble (UE0 alters UL Tx beam during next PRACHoccasion).

Here, it should be noted that although the gNB detects the MSG1 ofdifferent UEs, it may not confirm whether the MSG1 is transmitted fromdifferent UEs and a collision occurs because the MSG2 cannot betransmitted to different UEs. That is, a beamforming-based random accessprocedure (RA procedure) needs to be defined in consideration of a beam,a RACH transmission resource (RACH transmission resource), and apreamble ID or the like in an LTE-based RA procedure.

A second method for establishing a relationship between MSG2 and MSG1 isa method for transmitting the transmission beam (Tx beam) informationincluding the MSG2. At this time, the transmission beam information maymean transmission beam information of a wireless transmitting andreceiving device, such as the base station, the terminal, the relay, abackhaul, and a transmission and reception point (TRP).

The terminal may detect the transmission beam (Tx beam) informationincluded in the MSG2 to determine whether the received MSG2 correspondsto the MSG1 transmitted by the corresponding terminal. The transmissionbeam level may be divided into the transmission beam of the base stationand the transmission beam of the terminal as follows.

When the transmission beam information included in the MSG2 is thetransmission beam used when the terminal transmits the MSG1, theterminal may confirm that the MSG2 received is for the MSG1 transmittedby the terminal. Accordingly, the terminal may transmit the MSG3 usingthe uplink resource allocation information included in the MSG2. Inaddition, the terminal may transmit the MSG 3 using the terminal beamincluded in the MSG2.

When the transmission beam information included in the MSG2 is thetransmission beam of the base station, the terminal may transmit thebase station beam information estimated when receiving the downlinksynchronization signal by including the base station beam information inthe MSG1. Through this information, the terminal may confirm that thereceived MSG2 is for the MSG1 transmitted by the terminal. Accordingly,the terminal may transmit the MSG3 using the uplink resource allocationinformation included in the MSG2. Also, the terminal may transmit theMSG3 using the beam of the terminal corresponding to the transmissionbeam of the base station.

For this purpose, the base station should be able to estimate thetransmission beam (Tx beam) of the base station, the terminal, or otherequipment while detecting the RACH in the step of transmitting the MSG1.As the method for the base station to detect the ID of the Tx beam inthe step of transmitting the MSG1, the following method may beconsidered.

1. A method for allowing a set for RA sequences to include Tx beaminformation

2. A method for allowing a subset of RACH resources to include Tx beaminformation

3. A method for allowing a time domain OCC index to include Tx beaminformation

4. A method for allowing a combination of preamble index to include Txbeam information

The first method of transmitting the Tx beam information to the basestation in the step of transmitting the MSG1 may include a method forincreasing the number of RA sequence sets by the number of Tx beam IDs.That is, if the existing LTE has 64 preamble IDs in one cell, the firstmethod may set the preamble ID by 64×N (the number of Tx beams). On theother hand, since the number of Tx beams of the terminal may bedifferent for each terminal or each base station, it is possible tolimit the maximum number of Tx beams and define a sequence setaccordingly.

A second method of transmitting Tx beam information to a base station inthe step of transmitting the MSG1 is a method for allowing the RACHresource to include Tx beam information. As shown in FIG. 3B, a timeresource of the subset of RACH resources is already associated with theDL signal/channel. Here, the Tx beam information may be included in afrequency index so that the subset of RACH resources may include the Txbeam information.

FIG. 9 is a diagram illustrating a method for allowing an RACH resourceto include Tx beam information.

As shown in FIG. 9, a frequency index of a subset of different RACHresources may include Tx beam information.

A third method for transmitting Tx beam information to a base station inthe step of transmitting the MSG1 is a method for allowing a time domainOCC index to include Tx beam information. As described above, as amethod for increasing capacity, an orthogonal cover code may be appliedover several RACH OFDM symbols or RACH sequences. At this time, theindex of the orthogonal cover code may include the Tx beam information.For example, when considering a preamble for transmitting a plurality ofRACH symbols, the time domain OCC may be applied to a plurality ofpreambles having the same preamble identifier. At this time, if thereare M OCC indices corresponding to the number N of transmission beams,each OCC index may denote a transmission beam set corresponding to N/M.

A fourth method for transmitting Tx beam information to a base stationin the step of transmitting the MSG1 is a method for allowing acombination of preamble identifiers to include Tx beam information. Forexample, when considering a preamble for transmitting a plurality ofRACH symbols, a plurality of preambles may have different preambleidentifiers. If the combination of each preamble identifiers correspondsto the number N of transmission beams, the base station may determinewhich transmission beam was used when the base station detects thecombination of preamble identifiers.

A third method for establishing a relationship between MSG2 and MSG1 isa method for setting a time between MSG1 and MSG2.

FIGS. 10A and 10B are diagrams showing a method for setting a timebetween MSG2 and the MSG1.

Referring to FIG. 10A, after the terminal transmits the MSG1, it may beset to receive the MSG2 after a certain time. Therefore, when theterminal transmits the MSG1 and then receives the MSG2 after a certaintime, the terminal may recognize a response message to the MSG1transmitted by the terminal.

In this case, the terminal may transmit the MSG3 using the uplinkallocation information included in the MSG2 if there is MSG2 decoded fora predetermined second time after a predetermined first time based onthe RACH resource that transmits the MSG1.

Referring to FIG. 10A, the terminal may attempt to decode the MSG2 for asecond time T3 at a time point when a first time T2 has elapsed in eachRACH resource. This figure shows T3 based on a time point when the MSG1is transmitted in the first RACH resource, but it is obvious that the T3interval may be changed.

Accordingly, if the MSG2 received from the base station is received andthus the decoding is successful in the T3 interval, the terminal maytransmit the MSG3 using the uplink resource allocation informationincluded in the MSG2.

On the other hand, if the MSG2 is not received after the predeterminedtime (or there is no MSG2 being decoded) and the MSG2 is received at atime other than the time set for the MSG2 to be received, it may berecognized that the MSG2 is not a response message to the MSG1 of theterminal.

Therefore, the base station may retransmit the MSG1 after apredetermined time T1′ has elapsed.

Meanwhile, the base station may transmit the information on thepredetermined time to the terminal. For example, the base station mayset the MSG2 to receive the MSG2 after a predetermined time or apredetermined subframe after the terminal transmits the MSG1, and theinformation on the predetermined time or the predetermined subframe mayinclude RACH configuration information transmitted through the SIB orthe MIB. Alternatively, the information may be transmitted to theterminal through a high layer (e.g., RRC layer).

Meanwhile, the terminal may transmit the MSG3 using the uplinkallocation information included in the MSG2 if there is the MSG2 decodedfor the predetermined second time after the predetermined first time forthe MSG1 transmitted during the RACH transmission occasion based on theRACH transmission occasion.

Referring to FIG. 10B, the terminal may attempt to decode the MSG2 forthe second time T3 at a time point when the first time T2 has elapsedbased on the time point when the MSG1 is transmitted at the first RACHresource. However, in this case, the situation in which the MSG1transmitted from each RACH resource included in the RACH transmissionoccasion is not be identified may occur.

Accordingly, in the case in which the MSG2 received from the basestation is received and thus the decoding succeeds in the T3 interval,when the terminal may transmit the MSG3 using the uplink resourceallocation information included in the MSG2, the collision of the MSG3may occur.

On the other hand, if the MSG2 is not received after the predeterminedtime (or there is no MSG2 being decoded) and the MSG2 is received at atime other than the time set for the MSG2 to be received, it may berecognized that the MSG2 is not a response message to the MSG1 of theterminal.

Therefore, the base station may retransmit the MSG1 after apredetermined time T1′ has elapsed.

Meanwhile, the base station may transmit the information on thepredetermined time to the terminal. For example, the base station mayset the MSG2 to receive the MSG2 after a predetermined time or apredetermined subframe after the terminal transmits the MSG1, and theinformation on the predetermined time or the predetermined subframe mayinclude RACH configuration information transmitted through the SIB orthe MIB. Alternatively, the information may be transmitted to theterminal through a high layer (e.g., RRC layer).

The time shown in FIG. 10B may be defined as shown in Table 3.

TABLE 3 Transmission and processing time of MSG1 and MSG2 in RAprocedure Timeline Description T Time at MSG 1 transmission T₁ One RACHoccasion T₂ Delay from the time that MSG 1 transmission to the time UEstarts decoding MSG 2 T₃ Window for MSG 2 decoding T₁′ Time at MSG 1re-transmission

The information included in Table 3 may be transmitted to the terminalthrough the RACH configuration information transmitted through the SIBor the MIB. Alternatively, the information may be transmitted to theterminal through RRC layer signaling.

T denotes the time point when the MSG1 is transmitted. T may beconfigured according to the RACH configuration information.

T1 denotes the time of one RACH occasion.

T2 denotes a delay time until the decoding is performed after theterminal receives the MSG2.

T3 denotes a window for receiving the MSG2. That is, T3 means the timewhen the MSG2 is assumed to be received for a predetermined number n ofsubframes after a predetermined subframe after the transmission of theMSG1. Here, the predetermined number n may be informed the terminalthrough the RACH configuration information transmitted from the SIB/MIB.

However, when it is assumed that a subset of ‘M’ RACH resources isutilized at one RACH transmission occasion, the situation in which anRACH preamble transmitted through a subset of m-th (0<m≤M) RACH resourceand an RACH preamble transmitted through a subset of a k-th (0<k≤M) RACHresource are not identified occurs.

The following describes the situation in which the collision occurs. Theaccess probability when the MSG1 transmission is attempted m times maybe defined as follows.

${P_{m}^{a}(k)} = {1 - {\prod\limits_{i = 1}^{m}\;\left( {{P_{i}^{dm}(k)} + {\left( {1 - {P_{i}^{dm}(k)}} \right) \times {P_{c}(k)}}} \right)}}$

Here, (⋅) (k), n_(s,m), n_(d,m), n_(d) and n_(a) are the valuescollected during the time between [(k−1) T, kT], the number of RACHpreamble transmitted during the attempt time m times, the number of RACHpreambles detected during the attempt time m times, the number ofdetected RACH preambles, and the number of terminals that succeeds inRA.

The detection failure probability at the time of performing the attemptm times is as follows.

${P_{m}^{dm}(k)} = \left\{ \begin{matrix}{{1 - \frac{n_{d,m}(k)}{n_{s,m}(k)}},} & {n_{s,m} > 0} \\{0,} & {n_{s,m} = 0}\end{matrix} \right.$

In this case, a contention ratio may be represented as follows.

${P_{c}(k)} = \left\{ {\begin{matrix}{{1 - \frac{n_{a}(k)}{n_{d}(k)}},} & {n_{d} > 0} \\{0,} & {n_{d} = 0}\end{matrix}.} \right.$

That is, in order to reduce the collision probability, a scheme that canreduce the contention ratio is needed. It is the same as raising theprobability that the terminal succeeds in RA by the detected RACHpreamble. To this end, the contention ratio may be lowered according tothe method for setting the time relationship, which is the third methodamong the methods for establishing a relationship between MSG1 and MSG2described above.

Meanwhile, as shown in FIG. 10A, the method for establishing arelationship between MSG2 and MSG1 may be designed in consideration ofone or a plurality of RACH resources (RACH resources) in the RACHtransmission occasion as shown in Table 4 below.

TABLE 4 Method for establishing a relationship between MSG1 and MSG2 inbeamforming system Timeline Description T Time at MSG 1 transmissionT_(1, k) k-th subset of RACH resource in one RACH occasion T₂ Delay fromthe time that MSG 1 transmission to the time UE starts decoding MSG 2 T₃Window for MSG 2 decoding T₁′ Time at MSG 1 re-transmission

The time T1 shown in Table 3 denotes one RACH transmission occasionwhile T_(1,k) shown in Table 4 may include a time index of a subset ofRACH resources within one RACH transmission occasion.

That is, a plurality of subsets of RACH resources may be included in oneRACH transmission occasion, and T_(1,k) may denote an index of aplurality of subsets of RACH resources. Therefore, the terminaltransmitting the MSG1 in the RACH resource subset indicated by the indexmay decode the MSG2 for the T3 time after the T2 time, and if there isthe MSG2 decoded for the T3 time, the MSG3 may be transmitted using theuplink resource allocation information included in the MSG2. On theother hand, if there is no MSG2 to be decoded, the MSG1 may beretransmitted after T1′ time.

The fourth method for establishing the relationship between MSG1 andMSG2 is a method for using a preamble ID. In the present disclosure, thepreamble ID may mean a preamble sequence. The method for using apreamble ID may be generated as follows in consideration of a subset ofRACH resources.

1. Designed so that the Preamble ID includes a time index of a subset ofRACH resources

2. Designed so that the Preamble ID includes a frequency index of asubset of RACH resources

3. Designed so that the Preamble ID includes a frequency/time index of asubset of RACH resources

The RACH preamble ID in the LTE is generated as follows. In the LTE, 64preamble IDs are operated, and the terminal may select a root index forgenerating a preamble sequence (RACH OFDM symbol) through parameterstransmitted in the SIB2 (base sequence). The terminal may extend thepreamble ID according to a cyclic shift value interval (Ncs) based onthe selected root index. At the root index for one RACH OFDM symbol, ifthe number of preamble IDs extended by the CS value is less than 64, theterminal selects the next root index to extend the preamble ID.Similarly, even in the extended root index, the preamble ID is extendedaccording to Ncs. In this way, a total of 64 preamble IDs are generated.

The method for generating a preamble ID according to the presentdisclosure may be generated by extending the time or frequency index ofthe subset of RACH resources in the method for generating a preamble IDin LTE. In the case of the preamble format 1 shown in the above Table 1,the preamble ID may be generated by the same manner as the LTE.

In the case of the preamble format 2 (2.1˜2.5) for the high frequencysystem, it is difficult to extend the preamble ID in the same manner asthe LTE. The reason is that the spacing between the sub carriers is verylarge compared to the LTE as the symbol length is short, and thus it isdifficult to long allocate a length of the sequence in the frequencydomain as in the LTE. Therefore, when the root index for generatingdifferent preamble sequences (RACH OFDM symbols) is used in the sameresource, the influence of interference becomes very large, such thatthe number of root indexes used in the subset of RACH resources is verysmall, which means that it is difficult to extend the preamble ID as inthe LTE.

Therefore, as in the proposed method, the terminal may generate thepreamble ID including information indicating the RACH resource, suchthat the preamble ID may represent the relationship between the MSG1 andthe MSG2. Therefore, when the terminal detects the MSG2, the terminalmay determine based on which RACH resource the MSG1 transmissionsucceeds.

However, as described above, the information representing the RACHresource may be associated with the downlink signal or channel.Accordingly, in the present disclosure, the information representing thedownlink signal or channel may be used to generate the preamble ID. Forexample, the time or frequency index of the subframe that receives thedownlink synchronization signal may be used to generate the preamble ID.However, the embodiment of the present disclosure is not limitedthereto, and the subframe or the downlink signal receiving the referencesignal or the broadcast signal may be used to generate the preamble ID.

FIG. 11 is a diagram illustrating a relationship between MSG1 and MSG2depending on a preamble ID according to an embodiment of the presentdisclosure.

The UE0 and the UE1 may select the same root index and use the selectedroot index to generate the same preamble sequence. In addition, the UE0and the UE1 may transmit the MSG1 in the same subframe. Here, theembodiment in which the MSG1 is transmitted using the same subframe butusing a subset of different RACH resources is shown.

The base station may detect the preamble ID in different RACH resourceswhen receiving the RACH. Here, the base station in which the beamreciprocity is established may determine that different preamble IDs arethe preamble IDs transmitted from the different terminals. On the otherhand, the base station in which the beam reciprocity is not establishedmay not determine whether the preamble IDs detected in different RACHresources are RACH preamble IDs transmitted from the same terminal orRACH preamble IDs transmitted from different terminals.

Accordingly, the base station may assign an identifier (e.g., physicalID (PID)) according to the time or frequency index of the subset of RACHresources detected by the base station, and generate the RAR includingthe identifier and transmit the generated RAR to the terminal. Here, thetime or frequency index of the subset of the RACH resources may berepresented by the OFDM symbol index/slot index/subframe index of thetime when the RACH is transmitted, the starting point of the frequencydomain or the like.

Thus, by transmitting response messages including different PIDs to eachterminal even for the same preamble ID, the terminal may confirm whetheror not it is the response message transmitted to the terminal.

Referring to FIG. 11, the base station may transmit a RAR including PID0 to the UE0 and a RAR including PID1 to the UE1.

Accordingly, the terminal may detect the PID according to the preambleID used for the MSG1 transmission among the received RARs and select theMSG2 suitable for the terminal. That is, the terminal may decode theMSG2 to detect the PID, and transmit the MGS3 according to the uplinkresource allocation information included in the MSG2 in which the PIDcorresponding to the time or frequency index of the RACH resourcetransmitted by the MSG1 is detected.

A fifth method for establishing a relationship between MSG1 and MSG2 isa method for using RA-RNTI. The RA-RNTI is defined as follows in theLTE.RA-RNTI=1+t _(id) +f _(id)

-   -   where    -   t_(id): index of the first subframe (0<=t_(id)<10)    -   f_(id) location of PRACH transmission in frequency domain        (0<=f_(id)<=6)

The terminal transmitting the MSG1 monitors the PDCCH for the RAR. Thatis, the terminal monitors whether there is the RAR transmitted throughthe PDCCH. Here, the RAR transmitted through the PDCCH is divided intoRA-RNTIs. That is, the terminal may identify the PDCCH indicating theRAR to be transmitted to the terminal using the RA-RNTI.

When the terminal transmits the MSG1 using the same frequency resourcein the same subframe, the RA-RATI value is the same and the PDCCHaccording to the value is the same, such that the terminal decodes thePDCCH and decodes the MSG2 indicated by the PDCCH. That is, if theterminal uses the same preamble ID and transmits the MSG1 in the sameRA-RNTI, even if the base station detects the RACH in the subset ofdifferent RACH resources, the base station may not identify that theMSG1 is transmitted from different terminals.

Accordingly, in the present disclosure, a method for associating RA-RNTIwith a subset of different RACH resources and identifying MSG2 by aterminal will be described. A method for associating RA-RNTI with asubset of RACH resources is as follows.

1. A time index of a subset of RACH resources may be used to generatethe RA-RNTI.

RA-RNTI=1+t_id, t_id: Time index of a subset of RACH resources

2. A frequency index of a subset of RACH resources may be used togenerate the RA-RNTI.

RA-RNTI=1+f_id, f_id: Frequency index of a subset of RACH resources

3. A time or frequency index of a subset of RACH resources may be usedto generate the RA-RNTI.

RA-RNTI=1+t_id+f_id

4. A subframe index and a time or frequency index of a subset of RACHresources may be used to generate the RA-RNTI.

RA-RNTI=1+t_id+f_id+index of the subframe

However, as described above, the information representing the RACHresource may be associated with the downlink signal or channel.Accordingly, in the present disclosure, the information representing thedownlink signal or channel may also be used to generate the RA-RNTI. Forexample, the time or frequency index of the subframe that receives thedownlink synchronization signal may be used to generate the RA-RNTI.However, the embodiment of the present disclosure is not limitedthereto, and the subframe or the downlink signal receiving the referencesignal or the broadcast signal may be used to generate the RA-RNTI.

FIG. 12 is a diagram illustrating a relationship between the MSG1 andthe MSG2 depending on RA-RNTI according to an embodiment of the presentdisclosure.

FIG. 12 illustrates an embodiment for decoding a RAR when a time orfrequency index and a subframe index of a subset of RACH resources areassociated with RA-RNTI.

UE0 and UE1 transmit the same RACH preamble through a subset ofdifferent RACH resources. Therefore, the base station may detect thesame RACH sequence in different RACH resources. Here, the base stationin which the beam reciprocity is not established may not identifywhether it is an RACH sequence transmitted from different terminals oran RACH sequence transmitted from the same terminal. The base station inwhich the beam reciprocity is established may identify an RACH sequencetransmitted from different terminals. Since the Preamble ID (RACHsequence) is the same, the PID included in MSG2 is also the same.

However, in the case of using the above-described method, since the MSG1is transmitted in different RACH resources, the RA-RNTI may bedetermined differently for each terminal. Therefore, since the RA-RNTIsused for scrambling CRC of control information which points to the MSG2are different from each other, two terminals each may decode the controlinformation corresponding to the RA-RNTI suitable for the terminals. Inaddition, the MSG2 included in the control information can be decoded.

The sixth method for establishing a relationship between MSG1 and MSG2is a method for using a scrambling ID of MSG2. The following describesthe method for establishing a relationship between MSG1 and MSG2 usingthe scrambling ID of MSG2. The scrambling initial value is defined asfollows in the LTE.

$c_{init} = \left\{ \begin{matrix}{{n_{RNTI} \cdot 2^{14}} + {q \cdot 2^{13}} + {\left\lfloor {n_{s}/2} \right\rfloor \cdot 2^{9}} + N_{ID}^{cell}} & {{for}\mspace{14mu}{PDSCH}} \\{{\left\lfloor {n_{s}/2} \right\rfloor \cdot 2^{9}} + N_{ID}^{MBSFN}} & {{for}\mspace{14mu}{PMCH}}\end{matrix} \right.$

The scrambling ID may be determined according to the scrambling initialvalue determined as described above. Here, the MSG2 is transmitted onthe PDSCH. Here, n_RNTI represents an RNTI associated with PDSCH, qrepresents a codeword, ns represents a slot number, and NcellIDrepresents a cell ID.

Accordingly, the present disclosure proposes a method for applying PDSCHscrambling differently by using a subset of RACH resources whengenerating an initial value (Cinit) value. The terminal may decode theMSG2 suitable for the terminal by scrambling the MSG2 using differentscrambling.

Specifically, a method for associating a scrambling initial value with asubset of RACH resources is as follows

1. Use the time index of the subset of RACH resources to generate thescramble ID of the MSG2

2. Use the frequency index of the subset of RACH resources to generatethe scramble ID of the MSG2

3. Use the frequency or time index of the subset of RACH resources togenerate the scramble ID of the MSG2

However, as described above, the information representing the RACHresource may be associated with the downlink signal or channel.Accordingly, in the present disclosure, the information representing thedownlink signal or channel may also be used to generate the scramblingID. For example, the time or frequency index of the subframe thatreceives the downlink synchronization signal may be used to generate thescrambling ID. However, the embodiment of the present disclosure is notlimited thereto, and the subframe or the downlink signal receiving thereference signal or the broadcast signal may be used to generate thescrambling ID.

FIG. 13 is a diagram illustrating an operation sequence of a terminalaccording to an embodiment of the present disclosure.

Referring to FIG. 13, in step S1310, the terminal may transmit therandom access preamble to the base station.

The terminal may receive the system information through the broadcastchannel before transmitting the random access preamble, and the systeminformation may include random access related configuration information(RACH configuration information). The random access relatedconfiguration information may include the root index information forgenerating the random access preamble.

In addition, the random access related configuration information mayfurther include time information for use in decoding the above-describedresponse message or the like.

If the base station has the beam reciprocity, the terminal may transmitthe random access preamble in the RACH resource associated with thedownlink signal or channel. On the other hand, when the base stationdoes not have the beam reciprocity, the terminal may transmit the randomaccess preamble in the RACH transmission occasion including theplurality of RACH resources.

In step S1320, the terminal may receive the response message to therandom access preamble. The terminal may receive the response messageusing the selected reception beam while receiving the DL SS/BCH/BRS.

In step S1330, the terminal may decode the response message using theresource index to which the downlink signal is transmitted.Alternatively, the terminal may decode the response message using theindex of the resource including the downlink channel.

The terminal may perform the downlink synchronization by receiving thedownlink synchronization signal from the base station beforetransmitting the random access preamble, and the terminal may decode theresponse message based on the resource that receives the downlinksynchronization signal. Alternatively, the terminal may receive thesystem information, the broadcast information or the like from the basestation through the broadcast channel before transmitting the randomaccess preamble, and the terminal may decode the response message basedon the resource that receives the system information or the broadcastinformation.

The decoding step will be described in detail as follows.

The base station may transmit the response message including thetransmission beam information, and if the response message includesinformation corresponding to the transmission beam information of theterminal or the estimated transmission beam information of the basestation, the terminal may decode the message.

In this case, the transmission beam information may be associated with aresource index to which the downlink signal is transmitted or a resourceindex in which the downlink channel is included, and the terminal maydetermine the transmission beam information using the resource index towhich the downlink signal is transmitted or the resource index in whichthe downlink channel is included and decode the response message usingthe determined information.

Alternatively, the base station may define the time between the randomaccess preamble and the random access response message, and the terminalmay decode the random access response message when the random accessresponse message is received for the calculated time based on the timewhen the random access preamble is transmitted.

In this case, the resource transmitting the random access preamble maybe associated with the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded, and the terminal may determine the time when the random accesspreamble is transmitted and the time when the random access response isreceived based on the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded and confirm whether the response message is received bymonitoring the PDCCH for the time. Accordingly, if the response messageis received for the time, the terminal may recognize that the responsemessage is for the preamble transmitted by the terminal, and decode theresponse message.

Alternatively, when transmitting the random access preamble, theterminal may determine the RACH resource based on the preamble sequenceand transmit the determined RACH resource to the base station. Whendetermining the preamble sequence, the terminal may use the time orfrequency index of the resource to transmit the preamble.

In this case, the resource to transmit the preamble may be associatedwith the resource index to which the downlink signal is transmitted orthe resource index in which the downlink channel is included, and theterminal may determine the time or frequency when the random accesspreamble is transmitted based on the resource index to which thedownlink signal is transmitted or the resource index in which thedownlink channel is included and may generate the preamble sequenceusing the determined time or frequency and transmit the generatedpreamble sequence to the base station.

Accordingly, the base station may identify which RACH resource thereceived random access preamble is transmitted from, and may transmit tothe terminal the response message in which the physical identifier (PID)is differently allocated according to the time or frequency index of theRACH resource.

Accordingly, the terminal may decode the response message to detect thePID and determine whether it corresponds to the time or frequency indexof the RACH resource that transmits the random access preamble.

Alternatively, the terminal may scramble the control informationindicating the resource to which the response message is to betransmitted using the RA-RNTI determined based on the time or frequencyindex of the RACH resource. Specifically, the base station may scramblethe control information using the RA-RNTI generated using the time orfrequency index of the RACH resource to which the preamble istransmitted, and the terminal may descramble the control informationusing the RA-RNTI and decode the response message received at theresource indicated by the control information.

As described above, the resource to transmit the preamble may beassociated with the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded, and the terminal may determine the time or frequency to whichthe random access preamble is to be transmitted based on the resourceindex to which the downlink signal is transmitted or the resource indexin which the downlink channel is included and generate the RA-RNTI usingthe determined time or frequency to descramble the control information.The terminal may decode the response message in the resource indicatedby the descrambled control information.

Alternatively, the terminal may decode the response message using thescrambling ID determined based on the time or frequency index of theRACH resource. Therefore, the terminal may decode the response messageusing the scrambling ID determined based on the time or frequency indexof the RACH resource.

As described above, the resource to transmit the preamble may beassociated with the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded, and the terminal may determine the time or frequency to whichthe random access preamble is to be transmitted based on the resourceindex to which the downlink signal is transmitted or the resource indexin which the downlink channel is included and generate the scrambling IDusing the determined time or frequency to decode the response message.

After decoding the response message using the above method, the terminalmay transmit the RRC connection request message to the base station instep S1340. The terminal may transmit the RRC connection request messageusing the uplink resource allocation information included in theresponse message.

FIG. 14 is a diagram illustrating an operation sequence of a basestation according to an embodiment of the present disclosure.

Referring to FIG. 14, the base station may receive the random accesspreamble in step S1410. At this time, the plurality of terminals mayreceive the same random access preamble at one RACH transmissionoccasion. Therefore, the base station may identify the random accesspreamble to transmit the response message.

In step S1420, the base station may transmit the response message to therandom access preamble. At this time, the base station may includespecific information so that the terminal can identify the responsemessage, or process the message using the specific information. That is,the base station may generate the response message based on the specificinformation. At this time, the specific information may be determinedbased on a resource index to which the downlink signal is transmitted orthe resource index in which the downlink channel is included.

Accordingly, the terminal may decode the response message using theresource index to which the downlink signal is transmitted.Alternatively, the terminal may decode the response message using theresource index in which the downlink channel is included.

A process of transmitting a response message by the base station will bedescribed in detail as follows.

The base station may transmit the response message including thetransmission beam information. The base station may estimate thetransmission beam and include the estimated transmission beam in theresponse message.

In this case, the transmission beam information may be associated with aresource index to which the downlink signal is transmitted or a resourceindex in which the downlink channel is included, and the base stationmay determine the transmission beam information using the resource indexto which the downlink signal is transmitted or the resource index inwhich the downlink channel is included and include the determinedtransmission beam information in the response message.

Therefore, the response message may be decoded based on the resourceindex to which the downlink signal is transmitted or the resource indexin which the downlink channel is included.

Alternatively, the base station may define the time between the randomaccess preamble and the random access response message, and may transmitthe random access response message after a predetermined time in theRACH resource to which the corresponding preamble is transmitted.

In this case, the resource transmitting the random access preamble maybe associated with the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded, and the terminal may determine the time when the random accesspreamble is transmitted and the time when the random access response isreceived based on the resource index to which the downlink signal istransmitted or the resource index in which the downlink channel isincluded and confirm whether the response message is received bymonitoring the PDCCH for the time. Accordingly, if the response messageis received for the time, the terminal may recognize that the responsemessage is the preamble transmitted by the terminal, and decode theresponse message. That is, the response message may be decoded based onthe resource index to which the downlink signal is transmitted or theresource index in which the downlink channel is included.

Alternatively, when transmitting the random access preamble, theterminal may determine the RACH resource based on the preamble sequenceand transmit the determined RACH resource to the base station.Accordingly, the base station may identify which resource the preambleis transmitted using the received preamble sequence, and may transmit tothe terminal the response message in which the physical identifier (PID)is differently allocated according to the time or frequency index of thecorresponding resource.

In this case, the resource to which the preamble is to be transmittedmay be associated with the resource index to which the downlink signalis transmitted or the resource index in which the downlink channel isincluded, and the response message may be decoded based on the resourceindex to which the downlink signal is transmitted or the resource indexin which the downlink channel is included.

Alternatively, the base station may scramble the control informationusing the RA-RNTI generated using the time or frequency index of theRACH resource to which the preamble is transmitted. Therefore, theterminal may descramble the control information using the RA-RNTI anddecode the response message received from the resource indicated by thecontrol information.

As described above, the resource to which the preamble is to betransmitted may be associated with the resource index to which thedownlink signal is transmitted or the resource index in which thedownlink channel is included, and the response message may be decodedbased on the resource index to which the downlink signal is transmittedor the resource index in which the downlink channel is included.

Alternatively, the base station may scramble the response message usingthe scrambling ID determined based on the time or frequency index of theRACH resource. Therefore, the terminal may decode the response messageusing the scrambling ID determined based on the time or frequency indexof the RACH resource.

As described above, the resource to which the preamble is to betransmitted may be associated with the resource index to which thedownlink signal is transmitted or the resource index in which thedownlink channel is included, and the response message may be decodedbased on the resource index to which the downlink signal is transmittedor the resource index in which the downlink channel is included.

Also, the base station may include the uplink resource allocationinformation in the response message. Therefore, after transmitting theresponse message, the base station may receive the RRC connectionrequest message in step S1430. The base station may receive the RRCconnection request message from the resource according to the uplinkresource allocation information included in the response message.

FIG. 15 is a diagram illustrating a structure of the terminal accordingto an embodiment of the present disclosure.

Referring to FIG. 15, the terminal may include a transceiver 1510, acontroller 1520, and a memory 1530.

The transceiver 1510 may transmit/receive a signal to/from the basestation, and may include an interface unit for it. For example, thetransceiver 1510 may receive the random access related configurationinformation, a synchronization signal, transmit the random accesspreamble, and receive the response message thereto from the basestation.

The controller 1520 may control the operation of the terminal and maycontrol the terminal to perform the operations described in theembodiment. Also, the controller 1520 may include at least oneprocessor. Further, the processor may be controlled by a programincluding instructions that execute the methods described in theembodiments of the present specification. Further, the program may bestored in a storage medium, and the storage medium may include avolatile or non-volatile memory. The memory may be a medium capable ofstoring data, and the form thereof is not limited as long as it storesthe instructions.

More specifically, the controller 1520 may perform a control to transmitthe random access preamble to the base station. The controller 1520 mayreceive the response message to the random access preamble. The concretecontents in which the controller 1520 transmits and receives the randomaccess preamble are the same as those described above, and will beomitted below.

The controller 1520 may decode the response message using the resourceindex to which the downlink signal is transmitted. Alternatively, thecontroller 1520 may decode the response message using the resource indexin which the downlink channel is included.

The controller 1520 may perform the downlink synchronization byreceiving the downlink synchronization signal from the base stationbefore transmitting the random access preamble, and the controller 1520may decode the response message based on the resource that receives thedownlink synchronization signal. Alternatively, the controller 1520 mayreceive the system information, the broadcast information or the likefrom the base station through the broadcast channel before transmittingthe random access preamble, and the terminal may decode the responsemessage based on the resource that receives the system information orthe broadcast information.

The detailed content of the decoding step is the same as those describedabove and therefore will be omitted below.

After decoding the response message using the above method, thecontroller 1520 may transmit the RRC connection request message to thebase station. The controller 1520 may transmit the RRC connectionrequest message using the uplink resource allocation informationincluded in the response message.

FIG. 16 is a diagram illustrating a structure of the base stationaccording to an embodiment of the present disclosure.

Referring to FIG. 16, the base station may include a transceiver 1610, acontroller 1620, and a memory 1630.

The transceiver 1610 may transmit/receive a signal to/from the terminal,and may include an interface unit for it. For example, the transceiver1510 may transmit the random access related configuration informationand the synchronization signal to the terminal, receive the randomaccess preamble, and transmit the response message thereto.

The controller 1620 may control the operation of the terminal and maycontrol the terminal to perform the operations described in theembodiment. Also, the controller 1620 may include at least oneprocessor. Further, the processor may be controlled by a programincluding instructions that execute the methods described in theembodiments of the present specification. Further, the program may bestored in a storage medium, and the storage medium may include avolatile or non-volatile memory. The memory may be a medium capable ofstoring data, and the form thereof is not limited as long as it storesthe instructions.

More specifically, the controller 1620 may receive the random accesspreamble. At this time, the plurality of terminals may receive the samerandom access preamble at one RACH transmission occasion. Therefore, thebase station may identify the same to transmit the response message.

The controller 1620 may transmit the response message to the randomaccess preamble. At this time, the controller 1620 may include thespecific information so that the terminal can identify the responsemessage, or process the message using the specific information. That is,the base station may generate the response message based on the specificinformation. At this time, the specific information may be determinedbased on a resource index to which the downlink signal is transmitted orthe resource index in which the downlink channel is included.

The concrete contents of the process of transmitting, by the controller1620, a response message are the same as those described above, and willbe omitted below.

Also, the controller 1620 may include the uplink resource allocationinformation in the response message. Therefore, after transmitting theresponse message, the controller 1620 may receive the RRC connectionrequest message. The controller 1620 may receive the RRC connectionrequest message from the resource according to the uplink resourceallocation information included in the response message.

Meanwhile, although the exemplary embodiments of the present disclosurehave been illustrated in the present specification and the accompanyingdrawings and specific terms have been used, they are used in a generalmeaning in order to assist in the understanding the present disclosureand do not limit the scope of the present disclosure. It is obvious tothose skilled in the art to which the present disclosure pertains thatvarious modifications may be made without departing from the scope ofthe present disclosure, in addition to the exemplary embodimentsdisclosed herein.

The invention claimed is:
 1. A method performed by a terminal in awireless communication system, the method comprising: receiving, from abase station, system information including random access channel (RACH)configuration information; transmitting, to the base station, a randomaccess preamble in a RACH occasion based on the RACH configurationinformation, wherein the RACH occasion corresponds to a synchronizationsignal block (SSB) on which a downlink synchronization signal isreceived; and receiving, from the base station, a random access response(RAR) message as a response to the random access preamble, wherein theRAR message is decoded based on a random access-radio network temporaryidentifier (RA-RNTI), which is determined based on the RACH occasion. 2.The method of claim 1, wherein the RA-RNTI is determined based on a timeindex of the RACH occasion and a frequency index of the RACH occasion.3. The method of claim 1, wherein the RAR message is decoded based onbeam information, which is determined based on the SSB on which thedownlink synchronization signal is received.
 4. The method of claim 1,wherein the RAR message is decoded in case that the RAR message isreceived at a time corresponding to a time index of the RACH occasion inwhich the random access preamble is transmitted and time informationincluded in the RACH configuration information.
 5. A method performed bya base station in a wireless communication system, the methodcomprising: transmitting system information including random accesschannel (RACH) configuration information; receiving, from a terminal, arandom access preamble in a RACH occasion corresponding to asynchronization signal block (SSB) on which a downlink synchronizationsignal is transmitted; and transmitting, to the terminal, a randomaccess response (RAR) message in response to the random access preamble,wherein the RAR message is encoded based on a random access-radionetwork temporary identifier (RA-RNTI), which is determined based on theRACH occasion in which the random access preamble is received.
 6. Themethod of claim 5, wherein the RA-RNTI is determined based on a timeindex of the RACH occasion and a frequency index of the RACH occasion.7. The method of claim 5, wherein the RAR message is encoded in casethat the RAR message is transmitted at a time corresponding to a timeindex of the RACH occasion in which the random access preamble istransmitted and time information included in the RACH configurationinformation, and wherein the RAR message is encoded based on beaminformation, which is determined based on the SSB on which the downlinksynchronization signal is transmitted.
 8. A terminal in a wirelesscommunication system, the terminal comprising: a transceiver; and acontroller configured to: receive, via the transceiver from a basestation, system information including random access channel (RACH)configuration information, transmit, via the transceiver to the basestation, a random access preamble in a RACH occasion based on the RACHconfiguration information, wherein the RACH occasion corresponds to asynchronization signal block (SSB) on which a downlink synchronizationsignal is received, and receive, via the transceiver from the basestation, a random access response (RAR) message as a response to therandom access preamble, wherein the RAR message is decoded based on arandom access-radio network temporary identifier (RA-RNTI), which isdetermined based on the RACH occasion.
 9. The terminal of claim 8,wherein the RA-RNTI is determined based on a time index of the RACHoccasion and a frequency index of the RACH occasion.
 10. The terminal ofclaim 8, wherein the RAR message is decoded based on beam information,which is determined based on the SSB on which the downlinksynchronization signal is received.
 11. The terminal of claim 8, whereinthe RAR message is decoded in case that the RAR message is received at atime corresponding to a time index of the RACH occasion in which therandom access preamble is transmitted and time information included inthe RACH configuration information.
 12. A base station in a wirelesscommunication system, the base station comprising: a transceiver; and acontroller configured to: transmit, via the transceiver, systeminformation including random access channel (RACH) configurationinformation, receive, via the transceiver from a terminal, a randomaccess preamble in a RACH occasion corresponding to a synchronizationsignal block (SSB) on which a downlink synchronization signal istransmitted, and transmit, via the transceiver to the terminal, a randomaccess response (RAR) message in response to the random access preamble,wherein the RAR message is encoded based on a random access-radionetwork temporary identifier (RA-RNTI), which is determined based on theRACH occasion in which the random access preamble is received.
 13. Thebase station of claim 12, wherein the RA-RNTI is determined based on atime index of the RACH occasion and a frequency index of the RACHoccasion.
 14. The base station of claim 12, wherein the RAR message isencoded based on beam information, which is determined based on the SSBon which the downlink synchronization signal is transmitted.
 15. Thebase station of claim 12, wherein the RAR message is encoded in casethat the RAR message is transmitted at a time corresponding to a timeindex of the RACH occasion in which the random access preamble istransmitted and time information included in the RACH configurationinformation.